Imvelaphi yoPhando
Njengomthombo wendalo, omninzi novuselelekayo, i-cellulose idibana nemingeni emikhulu kwizicelo ezisebenzayo ngenxa yeempawu zayo zokunganyibiliki kunye nokuncitshiswa okulinganiselweyo. Ukuqina okuphezulu kunye neebhondi ze-hydrogen ezinoxinano oluphezulu kwisakhiwo se-cellulose zenza ukuba yonakale kodwa inganyibiliki ngexesha lenkqubo yokubamba, kwaye inganyibiliki emanzini nakwizinto ezininzi ezinyibilikayo. Izinto eziphuma kuzo ziveliswa yi-esterification kunye ne-etherification yamaqela e-hydroxyl kwiiyunithi ze-anhydroglucose kwikhonkco le-polymer, kwaye ziya kubonisa ezinye iimpawu ezahlukeneyo xa kuthelekiswa ne-cellulose yendalo. I-etherification reaction ye-cellulose inokuvelisa ii-ethers ezininzi ze-cellulose ezinyibilikayo emanzini, ezifana ne-methyl cellulose (MC), i-hydroxyethyl cellulose (HEC) kunye ne-hydroxypropyl cellulose (HPC), ezisetyenziswa kakhulu ekutyeni, kwizithambiso, kumayeza nakumayeza. I-CE enyibilikayo emanzini inokwenza ii-polymers ezibophelelwe yi-hydrogen kunye nee-polycarboxylic acids kunye nee-polyphenols.
Indibano yeLayer-by-layer (LBL) yindlela esebenzayo yokulungiselela iifilimu ezincinci zepolymer composite. Oku kulandelayo kuchaza ikakhulu indibano yeLBL yee-CE ezintathu ezahlukeneyo ze-HEC, MC kunye ne-HPC kunye ne-PAA, kuthelekisa indlela eziziphatha ngayo indibano, kwaye kuhlalutywa impembelelo yezinto ezithatha indawo kwindibano ye-LBL. Phanda impembelelo ye-pH kubukhulu befilimu, kunye nomahluko owahlukileyo we-pH ekwakhiweni kwefilimu nasekunyibilikeni kwayo, kwaye uphuhlise iipropati zokufunxa amanzi ze-CE/PAA.
Izixhobo zovavanyo:
I-Polyacrylic acid (PAA, Mw = 450,000). I-viscosity yesisombululo samanzi esingu-2wt.% se-hydroxyethylcellulose (HEC) yi-300 mPa·s, kwaye inqanaba lokutshintshwa yi-2.5. I-Methylcellulose (MC, isisombululo samanzi esingu-2wt.% esine-viscosity engama-400 mPa·s kunye nenqanaba lokutshintshwa kwe-1.8). I-Hydroxypropyl cellulose (HPC, isisombululo samanzi esingu-2wt.% esine-viscosity engama-400 mPa·s kunye nenqanaba lokutshintshwa kwe-2.5).
Ukulungiswa kwefilimu:
Ilungiselelwe ngendibano yekristale yolwelo kwi-silicon kwi-25°C. Indlela yokunyanga ye-slide matrix yile ilandelayo: faka kwisisombululo se-asidi (H2SO4/H2O2, 7/3Vol/VOL) imizuzu engama-30, uze uhlambe ngamanzi acocekileyo amaxesha amaninzi de i-pH ibe ne-neutral, uze ekugqibeleni wome nge-nitrogen ecocekileyo. Indibano ye-LBL yenziwa kusetyenziswa oomatshini abazenzekelayo. I-substrate ifunxwe ngokutshintshiselana kwisisombululo se-CE (0.2 mg/mL) kunye nesisombululo se-PAA (0.2 mg/mL), isisombululo ngasinye sifunxwe imizuzu emi-4. Ukuhlamba kathathu komzuzu omnye emanzini acocekileyo kwenziwa phakathi kokucwilisa isisombululo ngasinye ukususa i-polymer enamathele ngokukhululekileyo. Amaxabiso e-pH yesisombululo sendibano kunye nesisombululo sokuhlambulula zombini zilungiswe kwi-pH 2.0. Iifilimu ezilungisiweyo zichazwa njenge-(CE/PAA)n, apho u-n ubonisa umjikelo wendibano. (HEC/PAA)40, (MC/PAA)30 kunye (HPC/PAA)30 zilungiselelwe ikakhulu.
Ukuchazwa kweempawu zefilimu:
Iispectra zokubonakalisa eziphantse zibe zesiqhelo zarekhodwa zaza zahlalutywa ngeNanoCalc-XR Ocean Optics, kwaye ubukhulu beefilimu ezifakwe kwisilicon balinganiswa. Nge-substrate yesilicon engenanto njengemvelaphi, i-spectrum ye-FT-IR yefilimu encinci kwi-substrate yesilicon yaqokelelwa kwi-spectrometer ye-infrared ye-Nicolet 8700.
Ukusebenzisana kwebhondi ye-hydrogen phakathi kwe-PAA kunye ne-CEs:
Ukuhlanganiswa kwe-HEC, MC kunye ne-HPC kunye ne-PAA kwiifilimu ze-LBL. Iispectra ze-infrared ze-HEC/PAA, MC/PAA kunye ne-HPC/PAA ziboniswe kumfanekiso. Imiqondiso ye-IR enamandla ye-PAA kunye ne-CES inokubonwa ngokucacileyo kwi-spectra ye-IR ye-HEC/PAA, MC/PAA kunye ne-HPC/PAA. I-spectroscopy ye-FT-IR inokuhlalutya ukuhlanganiswa kwebhondi ye-hydrogen phakathi kwe-PAA kunye ne-CES ngokujonga utshintsho lweebhendi zokufunxa iimpawu. Ukuhlanganiswa kwe-hydrogen phakathi kwe-CES kunye ne-PAA kwenzeka kakhulu phakathi kwe-hydroxyl oxygen ye-CES kunye neqela le-COOH le-PAA. Emva kokuba ibhondi ye-hydrogen yenziwe, ubomvu obuthambileyo butshintshela kwicala eliphantsi le-frequency.
Incopho ye-1710 cm-1 yabonwa kwi-powder ye-PAA ecocekileyo. Xa i-polyacrylamide yahlanganiswa yaba ziifilimu ezinee-CE ezahlukeneyo, iincopho zeefilimu ze-HEC/PAA, MC/PAA kunye ne-MPC/PAA zazikwi-1718 cm-1, 1720 cm-1 kunye ne-1724 cm-1, ngokwahlukeneyo. Xa kuthelekiswa ne-powder ye-PAA ecocekileyo, ubude bencopho beefilimu ze-HPC/PAA, MC/PAA kunye ne-HEC/PAA butshintshiwe nge-14, 10 kunye ne-8 cm−1, ngokwahlukeneyo. I-hydrogen bond phakathi kwe-ether oxygen kunye ne-COOH iphazamisa i-hydrogen bond phakathi kwamaqela e-COOH. Okukhona ii-hydrogen bonds ezininzi zenziwa phakathi kwe-PAA kunye ne-CE, kokukhona i-CE/PAA itshintsha kakhulu kwi-IR spectra. I-HPC inezinga eliphezulu le-hydrogen bond complexation, i-PAA kunye ne-MC ziphakathi, kwaye i-HEC yeyona iphantsi.
Ukuziphatha okukhulayo kweefilimu ezidityanisiweyo ze-PAA kunye ne-CEs:
Indlela yokuziphatha kwe-PAA kunye nee-CEs ezenzela ifilimu ngexesha lokuhlanganiswa kwe-LBL iphandwe kusetyenziswa i-QCM kunye ne-spectral interferometry. I-QCM iyasebenza ekujongeni ukukhula kwefilimu kwindawo ethile ngexesha lemijikelo embalwa yokuqala yokuhlanganiswa. Ii-spectral interferometers zifanelekile kwiifilimu ezikhuliswe ngaphezulu kwemijikelo eli-10.
Ifilimu ye-HEC/PAA ibonise ukukhula okuthe tye kuyo yonke inkqubo yokuhlanganisa i-LBL, ngelixa iifilimu ze-MC/PAA kunye ne-HPC/PAA zibonise ukukhula okuthe tye kwizigaba zokuqala zokuhlanganisa zaza zaguquka zaba kukukhula okuthe tye. Kwindawo yokukhula okuthe tye, okukhona inqanaba lobunzima liphezulu, kokukhona ukukhula kobukhulu kumjikelo ngamnye wokuhlanganisa kukhulu.
Impembelelo yesisombululo se-pH ekukhuleni kwefilimu:
Ixabiso le-pH yesisombululo lichaphazela ukukhula kwefilimu ye-polymer edibeneyo ye-hydrogen. Njenge-polyelectrolyte ebuthathaka, i-PAA iya kuba yi-ionized kwaye itshajwe kakubi njengoko i-pH yesisombululo isanda, ngaloo ndlela ithintela umanyano lwe-hydrogen bond. Xa inqanaba le-ionization ye-PAA lifikelele kwinqanaba elithile, i-PAA ayikwazanga ukuhlanganiswa ibe yifilimu ene-hydrogen bond acceptors kwi-LBL.
Ubukhulu befilimu buyehla ngokonyuka kwe-pH yesisombululo, kwaye ubukhulu befilimu buyehla ngequbuliso kwi-pH2.5 HPC/PAA kunye ne-pH3.0-3.5 HPC/PAA. Ingongoma ebalulekileyo ye-HPC/PAA imalunga ne-pH 3.5, ngelixa eye-HEC/PAA imalunga ne-3.0. Oku kuthetha ukuba xa i-pH yesisombululo sokuhlanganiswa iphezulu kune-3.5, ifilimu ye-HPC/PAA ayinakwenziwa, kwaye xa i-pH yesisombululo iphezulu kune-3.0, ifilimu ye-HEC/PAA ayinakwenziwa. Ngenxa yomgangatho ophezulu we-hydrogen bond complexation ye-HPC/PAA membrane, ixabiso le-pH elibalulekileyo le-HPC/PAA membrane liphezulu kunele-HEC/PAA membrane. Kwisisombululo esingenatyuwa, amaxabiso e-pH abalulekileyo ee-complexes ezenziwe yi-HEC/PAA, i-MC/PAA kunye ne-HPC/PAA ayemalunga ne-2.9, 3.2 kunye ne-3.7, ngokwahlukeneyo. I-pH ebalulekileyo ye-HPC/PAA iphezulu kuneye-HEC/PAA, ehambelana neye-LBL membrane.
Ukusebenza kokufunxwa kwamanzi kwe-CE/PAA membrane:
I-CES ityebile kumaqela e-hydroxyl ukuze ibe nokufunxwa kakuhle kwamanzi kunye nokugcinwa kwamanzi. Ukuthatha i-membrane ye-HEC/PAA njengomzekelo, amandla okufunxwa kwe-membrane ye-CE/PAA ene-hydrogen ebotshelelwe emanzini kwindawo engqongileyo afundwe. Iphawulwa yi-spectral interferometry, ubukhulu befilimu buyanda njengoko ifilimu ifunxwa amanzi. Yabekwa kwindawo enomswakama ohlengahlengiswayo kwi-25°C kangangeeyure ezingama-24 ukuze kufezekiswe ukulingana kokufunxwa kwamanzi. Iifilimu zomiswa kwi-oven ye-vacuum (40°C) kangangeeyure ezingama-24 ukuze kususwe ngokupheleleyo ukufuma.
Njengoko umswakama usanda, ifilimu iyanda. Kwindawo enomswakama ophantsi we-30%-50%, ukukhula kobukhulu kucotha. Xa umswakama udlula i-50%, ubukhulu bukhula ngokukhawuleza. Xa kuthelekiswa ne-membrane ye-PVPON/PAA ene-hydrogen-bonded, i-membrane ye-HEC/PAA inokufunxa amanzi amaninzi kwindalo esingqongileyo. Phantsi kwemeko yomswakama ohambelanayo we-70% (25°C), uluhlu lokuqina lwefilimu ye-PVPON/PAA lumalunga ne-4%, ngelixa olo lwefilimu ye-HEC/PAA luphezulu malunga ne-18%. Iziphumo zibonise ukuba nangona inani elithile lamaqela e-OH kwinkqubo ye-HEC/PAA athathe inxaxheba ekwakhiweni kweebhondi ze-hydrogen, kwakusekho inani elikhulu lamaqela e-OH asebenzisana namanzi kwindalo esingqongileyo. Ke ngoko, inkqubo ye-HEC/PAA ineempawu ezilungileyo zokufunxa amanzi.
ukuququmbela
(1) Inkqubo ye-HPC/PAA enezinga eliphezulu le-hydrogen bonding ye-CE kunye ne-PAA inokukhula ngokukhawuleza phakathi kwazo, i-MC/PAA iphakathi, kwaye i-HEC/PAA yeyona iphantsi.
(2) Ifilimu ye-HEC/PAA ibonise indlela yokukhula ethe tye kuyo yonke inkqubo yokulungiselela, ngelixa ezinye iifilimu ezimbini i-MC/PAA kunye ne-HPC/PAA zibonise ukukhula okubonakalayo kwimijikelo embalwa yokuqala, zaza zaguqulwa zaba yindlela yokukhula ethe tye.
(3) Ukukhula kwefilimu ye-CE/PAA kuxhomekeke kakhulu kwi-pH yesisombululo. Xa i-pH yesisombululo iphezulu kuneyona nto ibalulekileyo, i-PAA kunye ne-CE azinakudibana zibe yifilimu. I-membrane ye-CE/PAA edibeneyo yayinyibilika kwizisombululo ze-pH ephezulu.
(4) Ekubeni ifilimu ye-CE/PAA ityebile kwi-OH kunye ne-COOH, unyango lobushushu lwenza ukuba idityaniswe. I-membrane ye-CE/PAA edityaniswe ne-cross-linked inozinzo oluhle kwaye ayinyibiliki kwizisombululo ze-pH ephezulu.
(5) Ifilimu ye-CE/PAA inomthamo ofanelekileyo wokufunxa amanzi kwindalo esingqongileyo.
Ixesha lokuthumela: Feb-18-2023